Products of this type are known in prior art and are used in particular as adjustment shims for mechanical assemblies. These assemblies generally have extensive play at certain points, resulting from the combination of manufacturing tolerances. This play is compensated for by insertion of shims.
The thickness of these shims is adjusted by removing the upper or lower sheets one by one until the desired thickness is reached.
These shims are used in particular in industries in which the complete traceability of all the parts is required for reasons of safety or quality assessment. This is the case, for example, in aeronautics. Each part constituting an aircraft is numbered, and a quality assessment file is associated with it containing the manufacturing plans or at least their references, the materials certificates, the references of the manufacturing specifications, etc.
The serial numbers of the peelable shims are generally marked in indelible ink by a stamp on the upper side of the shim at the time of manufacturing.
This technique has a number of defects.
The upper sheets of the shim bearing the serial number are removed during the operation of adjustment of the thickness of the shim. Once this operation is done, the shim can no longer be identified. It can be lost or interchanged by mistake with another one between the time its thickness is adjusted and the time it is positioned.
Furthermore, the marking is difficult to read on certain types of shims such as, for example, shims made of composite material, which have a surface which is unsuitable for stamping, smooth or hatched depending on the materials.
Finally, since the shims are generally small in size, the volume of information that can be marked on the shim is very small. It is generally limited to the serial number of the shim.